RFC3339 (similar to ISO 8601, but more strict) is great for computer readable use cases, but I've found it lacking for human use cases since there is still technically room for ambiguity and it's unfamiliar to most people. For anything like filling out a form that a person will read, I've started using the following:

12 Jun 2020

This is about as unambiguous as I can imagine for any person to read, and they require no familiarity with the format for it to be as such.